Study links mercury from power plants to autism

Published 5:30 am, Thursday, March 17, 2005

After years of debate about whether a nationwide explosion in autism is related to a mercury-based preservative used in vaccines, Texas researchers have found a new suspect: mercury from coal-burning power plants.

In a new study, scientists at the University of Texas Health Science Center at San Antonio are reporting a strong correlation between higher mercury release levels and the developmental disorder marked by communication and social interaction problems.

"This is a preliminary study that needs further study but suggests there is a link," said Raymond F. Palmer, an associate professor in the UT-San Antonio's department of family and community medicine and the study's lead author. "If corroborated, it would have pretty severe implications for policy."

Palmer called the study the first to examine the relationship between potentially chronic, low-dose exposure to mercury and developmental disorders such as autism. He stressed it does not prove causation.

The study, to be published in an upcoming edition of the journal Health and Place and already online, looked at 254 counties and 1,200 school districts in Texas, comparing 2001 mercury emission levels with rates of autism and special education services.

Using statistical modeling, Palmer's team found a 17 percent increase in autism rates for every 1,000 pounds of mercury released.

About 48 tons of mercury are released in the air annually in the United States from hundreds of coal-burning plants. Texas plants release more than those in any other state.

The study was undertaken amid uncertainty about a dramatic increase in autism. Once thought to occur in 1 of every 10,000 children, today it is estimated to afflict as many as 1 in 250.

The still poorly understood disorder has a strong genetic component, but the increase in cases has fueled theories the environment is playing a role. To some, mercury, a neurotoxin that affects the brain, spinal cord, kidneys and liver, made logical sense .

Suspicion initially fell upon vaccines, many of which use thimerosal, a mercury-based preservative. During the period reported autism rates grew, U.S. health authorities expanded the shots given to children, causing many parents to suspect the vaccine. But no proof was ever found; and last year, a controversial Institute of Medicine report concluded there is no causal link.

Dr. Sarah Spence, medical director of the UCLA Autism Evaluation Clinic, called the UT-San Antonio study "very interesting." She noted that the mercury released by power plants has known toxic effects on humans, whereas that's still speculative in the kind of mercury used in vaccines.

"If the statistical modeling in the study is accurate, it's an important first step," said Spence. "Proving causation would provide important information to both researchers and clinicians, who know people receiving treatment to remove mercury."

Susan West Marmagas, director of the Washington, D.C.-based Physicians for Social Responsibility's environment and health program, called the study "the kind of research the scientific community needs to better evaluate the potential links between mercury and autism," but said she would need to confer with experts before commenting further.

Palmer said his next step will be to look at associations between mercury emissions and autism rates over time, about 15 years. He will start with Texas data, then compare that to national numbers.

"If this study is corroborated, I would hope it leads to reductions, just as studies led to reductions in lead," said Palmer.

The Bush administration Tuesday ordered power plants to cut mercury pollution from smokestacks by nearly half within 15 years. Environmentalists complained that the order fell short of what was needed.